1. Field of the Invention
This invention relates to a life safety system and method that is energy efficient. In particular, the present invention relates to a life safety system and method for controlling a visual signal in an energy efficient manner.
2. Description of the Prior Art
Life safety systems are used in and around buildings to alert people of an emergency event, such as a fire or other event that could cause bodily harm. Generally, a life safety system includes one or more visual signals and/or audible signals that are operated to alert people of an emergency event and guide them along an evacuation route.
It is known to operate a visual signal in a continuous mode in which the visual signal flashes at a rate in the range of about 0.33 to 3 Hz with one flash per cycle. A continuous mode flashing is not very distinctive and may not sufficiently alert a hearing impaired person of impending danger. Also, such visual signals are designed to operate only in the continuous mode. That is, there is no provision for a user to choose another mode.
It is also known to operate an audible signal in either a continuous mode or in a temporal mode. In the continuous mode, the audible signal emits sound bursts at a rate of about 0.33 to 3 HZ with one sound burst per cycle. In the temporal mode, the audible signal operates in a sound pattern of four cycles with one sound burst per cycle for the first three cycles and no sound burst for the fourth cycle. The temporal mode is especially beneficial to the visually impaired person as it provides a distinctive and recognizable warning sound pattern.
It is also known to use one or more micro-controllers to control the operation of visual and/or audible signals. For example, U.S. Pat. No. 5,659,287 to Donati et al. provides a life safety system having a micro-controller that operates a visual signal and/or an audible signal based on program routines. The program routines include the capability of operation in a synchronous mode with other micro-controllers in the life safety system such that visual signals controlled by the micro-controllers all flash substantially in unison. The program routines also operate the audible signal in either a continuous mode or in a three pulse temporal pattern. However, the program routines make no provision for the micro-controller to operate the visual signal and the audible signal in synchronism so that a visual flash and a sound burst occur substantially simultaneously.
Accordingly, there is a need to provide a user of a life safety system with a choice of choosing a mode other than continuous for a visual signal. There is also a need to control the initiation of a visual signal annunciation and an audible signal annunciation so that they appear simultaneous in time to a person who is subjected to both. There is also a need to provide a distinctive visual flash pattern to a hearing impaired person for emergency event situations.
An object of the present invention is to provide a method of operating a visual signal that meets the aforementioned needs.
Another object of the present invention is to provide a life safety system that satisfies the above needs.
A method according to the present invention operates a visual signal in a life safety system. The life safety system includes a micro-controller that operates the visual signal to provide a visual alarm signal when an emergency event occurs.
The method determines if a temporal mode is set in the micro-controller. If a temporal mode is set, a flash pulse stream is developed that has a repetitive pattern of four cycles with one flash pulse per cycle for the first three cycles of the pattern and no flash pulse for the fourth cycle of the pattern. The flash pulse stream is then applied to the visual signal. The visual signal flashes in a repetitive pattern that includes four consecutive cycles with a flash occurring in each of the first three cycles of the pattern and no flash occurring in the fourth cycle. This eliminates a need for the visual signal to consume energy during the fourth cycle with the advantage that a smaller and less costly power supply can be used.
In another aspect of the invention, the micro-controller is controlled to cause the visual signal and an audible signal to flash and sound in unison.
A life safety system according to the present invention includes an energy saver program that causes the micro-controller to use the method of the present invention.